Dr. Krumholz found that the majority of 30-day readmissions for elderly patients with heart failure, pneumonia, or chronic obstructive pulmonary disease are for conditions other than the diagnosis named at discharge. He attributes this phenomenon to hospitalization-related sleep deprivation, malnourishment, pain and discomfort, cognition- and physical function-altering medications, deconditioning from bed rest or inactivity, and the experience of confronting stressful, mentally challenging situations in the hospital. Such stressors leave elderly patients with post-hospitalization disabilities comparable to a bad case of jet lag."

"To promote successful recovery after a hospitalization, health care professionals often focus on issues related to the acute illness that precipitated the hospitalization. Their disproportionate attention to the hospitalization's cause, however, may be misdirected. Patients who were recently hospitalized are not only recovering from their acute illness; they also experience a period of generalized risk for a range of adverse health events. Thus, their condition may be better characterized as a post-hospital syndrome, an acquired, transient period of vulnerability. This theory would suggest that the risks in the critical 30-day period after discharge might derive as much from the allostatic and physiological stress that patients experience in the hospital as they do from the lingering effects of the original acute illness. At the time of discharge, physiological systems are impaired, reserves are depleted, and the body cannot effectively defend against health threats."